In-line rheological testing of thermoplastics and a monitored device for an injection moulding machine: Application to raw and recycled polypropylene

A methodology for the rheological testing of polymers during the injection moulding process has been developed. This method has been designed to consider the non-conventional features of the plastication phase that result from the injection of recycled thermoplastics. The majority of previous research has been focused on extrusion machines or injection moulds. In this study, a measuring device is attached directly to the nozzle of the plasticising unit, enabling in-line measurements of the pressure drop and temperature that are necessary to calculate the apparent viscosity at different shear rates. Optimisation of the slit geometry also allows the production of parts without disturbing the operating parameters. The results have been corrected to characterise a mineral-filled polypropylene and its recycled form and to obtain the constants of its Carreau-WLF rheological model with SIM-Fit software. The material model constants have been implemented in Cadmould 3D-F simulation software. A comparison of the results with experimental injection moulding is consistent with the expected trends.